1. Field of the Invention
The present invention relates to a chip capacitor, a fabrication method for the same, and a metal mold.
2. Description of the Related Art
Japanese Unexamined Patent Application, First Publication No. Sho 60-66807 is a publication relating to a conventional capacitor. In this capacitor, a anode terminal embedded in the capacitor element is connected to a positive terminal, and provided with an external resin package with resin packaging provided such that the cathode terminal side of the capacitor element is connected to the negative terminal. In addition, Japanese Unexamined Patent Application, First Publication No. Sho 60-220921, is another publication related to conventional capacitors. This capacitor is provided with an external resin packaging such that the electrode surfaces on both sides of the capacitor element are connected to both terminals.
However, in recent years electronic devices such as mobile telephones require increasingly high functionality and at the same time decreasing weight, and the capacitors used in the electronic devices must also become smaller and more lightweight than they are at present.
In both of the above-described conventional capacitors, the packaging surface side of the terminal is flat, and the capacitors are soldered to printed circuit boards on this flat part. However, when the soldering is carried out using reflow soldering, there is the problem that what is termed the chip-standing phenomenon (also called the Manhattan phenomenon or the tombstone phenomenon), in which the component ends up standing on one end due to the surface tension of the solder, occurs easily. Furthermore, because this type of chip-standing phenomenon occurs particularly easily in ultra-small chips designed for small size and decreased weight, this is a problem that is inseparable from dealing with this type of small size and low weight design.
It is an object of the present invention to provide a chip capacitor, a fabrication method for the same, and a metal mold that can prevent the occurrence of the chip-standing phenomenon even when carrying out soldering using reflow soldering, and furthermore, can be adapted to reducing size and weight.
In order to attain this object, a first aspect of the invention is a chip capacitor having an external resin packaging formed such that a capacitor element is connected to both anode and cathode terminals thereof, wherein both or the terminals comprise a flat base plate that is exposed on the mounting surface side of the external resin packaging, connecting tongue pieces that rise relative to the flat plate and are connected to the capacitor element, and side piece parts that extend beyond the connecting tongue piece from the flat plate to the external end surface of the external resin packaging in a direction opposite to the flat plate, and further wherein ends of the side piece parts are exposed beyond their mounting surface sides to the external end surface of the external resin packaging at the diagonally rising side due to curved parts being formed by press processing that extend beyond the connecting tongue pieces rising in a diagonal direction relative to the connecting tongue pieces to the external end surface, and at the same time the mounting surface side is also exposed up to the external end surface.
In this manner, because curved parts being formed by press processing that extend beyond the connecting tongue pieces rising in a diagonal direction relative to the connecting tongue pieces to the external end surface, the side piece parts are exposed beyond the mounting surface to the external end surface of the external resin packaging at the side where the connecting tongue pieces rise, and at the same time, the mounting surface side is also exposed up to the external end surface.
Thereby, when the side piece parts are soldered to the printed circuit board by reflow soldering, the solder is trapped in the space under of the curved part of the side piece parts, and as a result, the occurrence of the chip-standing phenomenon can be prevented. Therefore, the occurrence of the chip-standing phenomenon can be prevented even when carrying out soldering using reflow soldering, and furthermore, this is in line with small size and decreasing weight.
Furthermore, because the curved parts are formed by press bending processing, fabrication is easy and the cost increases can be restrained.
In addition, because the structure has curved parts formed beyond the connecting tongue piece to the external end surface side of the external resin packaging, in other words, a structure in which the curved parts are interposed between the external end surface and the connecting tongue piece, a gap between the external end surface and the connecting tongue piece can be reliably opened, and positional relationships are attained in which the connecting tongue pieces can be reliably buried in the external resin packaging. As a result, the remarkable effects are attained that the capacitor element connected to a connecting tongue piece can be reliably buried in the external resin packaging, the moisture resistance can be maintained, and in particular, the leakage current characteristics can be maintained.
A second aspect of the chip capacitor of the present invention according to the first aspect is characterized in the curved parts having a bow shape.
In this manner, because the curved parts have a bow shape, the contact surface area in a curved part with the solder can be made large, and the reliability of the connection can be increased. In addition, because the curved parts are exposed, visual confirmation of the connection by the solder during packaging is easy.
A third aspect of the chip capacitor of the present invention according to the first and second aspect is characterized in the areas of both terminals exposed on the mounting surface side being equal to each other.
In this manner, because the areas of both terminals exposed to the mounting surface side are equal to each other, the contact area with the printed circuit board is equal, and as a result, the occurrence of the chip standing phenomenon during reflow soldering can be reliable prevented.
A fourth aspect of the chip capacitor of the present invention according to the first through third aspects is characterized in the height of the curved parts from the mounting surface being two times the height of the thickness of the base plate or greater.
In this manner, because the height of a curved part from the mounting surface is two times the height of the thickness of the base plate or greater, the solder can be sufficiently trapped in the space under the curved parts, and as a result, the occurrence of the chip standing phenomenon during reflow soldering can be reliably prevented.
A fifth aspect of the chip capacitor of the present invention according to the first through fourth aspects is characterized in the terminal of the cathode having a buried plate that is buried in the external resin packaging parallel to the base plate after being bent in the upward direction relative to the connecting tongue on the side of the base plate opposite to the side piece parts.
Thereby, because the terminal of the cathode is buried in the external resin packaging in the buried part parallel to the base plate in the upward direction relative to the connecting tongue piece, the occurrence of pealing of the terminal from the external resin packaging can be prevented.
A sixth aspect of the chip capacitor of the present invention according to the first through fifth aspects is characterized in a convex dam that projects to the capacitor element side and abuts the mounting surface side of the capacitor element being formed on the base plate.
In this manner, because a convex dam that projects to the capacitor element side and abuts the mounting surface side of the capacitor element is formed on the base plate, when the capacitor element and the base plate are attached using a conducting adhesive such as gold paste, unnecessary flowing out of the conducting adhesive can be prevented, and at the same time the thickness of the conducting adhesive becomes uniform and the disparities in the connection strength is eliminated.
A seventh aspect of the chip capacitor of the present invention according to the first through sixth aspects is characterized in the external resin packaging being formed by a liquid resin being printed using a squeegee.
In this manner, because the external resin packaging is formed by a liquid resin being printed using a squeegee, a metal transfer mold, which is expensive and difficult to fabricate, is not necessary, and as a result, the fabrication costs can be reduced, and at the same time design changes can be responded to immediately.
An eighth aspect of the chip capacitor of the present invention according to the first through sixth aspects is characterized in the external resin packaging being formed using a transfer mold formation method.
In this manner, because the external resin packaging is formed using a transfer mold formation method, the form of the external resin packaging can be stabilized.
A ninth aspect of the chip capacitor of the present invention according to the first through eighth aspects is characterized in a set of both an anode and cathode connected to the capacitor element being respectively provided on the two opposing surfaces of the external resin packaging.
Because both the anode and cathode connected to the capacitor element are respectively provided on the two opposing surfaces of the external resin packaging, there is a two-sided mounting structure and identifying the front and back during packaging becomes unnecessary, and at the same time, the arrangement of the connections overlapping in the thickness direction become easy to implement, and thus uses expand.
A fabrication method for a tenth aspect of a chip capacitor of the present invention is characterized in comprising a first press process that forms a pair of lead terminals by press formation on a flat lead frame so as to be opposite each other and at the same time a connecting tongue piece is formed by cutting out the center part of these lead terminals in the width direction, a second press process that forms convex curved parts by press formation that project in an upward diagonal direction relative to the connecting tongue piece to the side piece formation parts on both sides of the connection tongue pieces in the width direction, a connection process that connects the capacitor element to the connecting tongues of the pair of lead terminals, an external resin packaging process in which the mutually opposite sides of the pair of lead terminals and the capacitor element connected to the pair of lead terminals are integrated by an external resin packaging, and a cutting process that cuts the side piece formation parts at the middle position of the convex curved parts.
In this manner, in a first press process, a pair of lead terminals are formed on the flat lead frame so as to be opposite each other and at the same time connecting tongue pieces are formed by cutting out the center part of these lead terminals in the width direction; in a second press process, convex curved parts are formed that project in an upward diagonal direction relative to the connecting tongue pieces to the side piece formation parts on both sides of the connection tongue pieces in the width direction; in a connection process, the capacitor element is connected to the connecting tongues of the pair of lead terminals formed in the first process; in an external resin packaging process, the sides of the pair of lead terminals opposite to each other and the capacitor element connected to the pair of lead terminals are integrated by an external resin packaging; and in a cutting process, the side piece formation parts are cut at the middle position of the convex curved parts.
Thereby, by forming convex curved parts by a press process that curve in an upward diagonal direction relative to the connecting tongue pieces to the external end surface side of the external resin package beyond the connecting tongue to the side piece parts of the terminals, the side piece parts are exposed more in the upward diagonal direction on the external end surface than the mounting surface, and at the same time a shape can be easily formed for which the mounting surface also is exposed up to the end of the external resin packaging.
A fabrication method for a chip capacitor of an eleventh aspect of the present invention according to the tenth aspect is characterized in the external resin packaging being formed by a liquid resin being printed with a squeegee in the external resin packaging process.
In this manner, because the external resin packaging is formed by a liquid resin being printed with a squeegee in the external resin packaging process, a metal transfer mold, which is high cost and difficult to fabricate, becomes unnecessary, and as a result, fabrication costs can be reduced.
A fabrication method for a chip capacitor of a twelfth aspect of the present invention according to the eleventh aspect is characterized in providing the external resin packaging up to the outer side of the convex curved part of the side piece formation parts in the external resin packaging process, and cutting the external resin packaging on the plane that intersects the center position of the convex curved part of the side piece formation parts.
In this manner, because the external resin packaging is provided up to the outer side of the convex curved part of the side piece formation parts in the external resin packaging process and the external resin packaging is cut on the plane that intersects the center position of the convex curved part of the side piece formation parts, the elimination of the seams at the corners of the external resin packaging produced when the external resin packaging is formed by the liquid resin being printed with a squeegee and adjustment of the shape of the external resin packaging can be carried out in coordination with the cutting of the side piece formation parts.
A fabrication method of the chip capacitor of a twelfth aspect of the present invention according to the tenth aspect is characterized in the external resin packaging process providing the external resin packaging up to the center position of the convex curved part of the side piece formation parts by a transfer mold formation method.
In this manner, because the external resin packaging process provides the external resin packaging up to the center position of the convex curved part of the side piece formation parts by a transfer mold formation method, the shape can be adjusted without cutting the external resin packaging, and can be completed by cutting only the side piece formation parts.
A fabrication method of the chip capacitor of the fourteenth aspect of the present invention according to the thirteenth aspect is characterized in the formation of the convex curved parts in the second press process being carried out with the metal transfer mold used in the external resin packaging process.
In this manner, because the formation of the convex curved parts in the second press process are carried out with a metal transfer mold used in the external resin packaging process, the metal transfer mold can also be used as a metal press mold for the formation of the convex curved parts. Thus, the number of metal molds can be decreased, and the cost can be decreased.
A metal mold according to a fifteenth aspect of the present invention is used in an external resin packaging process of the fabrication method for a chip capacitor having a first formation process that forms by press formation a pair of lead terminals on a flat lead frame so as to be opposite to each other and forms connecting tongue pieces by cutting out the center part of these lead terminals in the width direction, a second process that forms convex curved parts by press formation that protrude in the upward diagonal direction relative to the connecting tongue piece to both of the side piece formation parts of the connecting tongue pieces in the width direction, a connection process that connects the capacitor element to a connecting tongue piece of the pair of lead terminals, an external resin packaging process that integrates with the external resin packaging the mutually opposite sides of the pair of lead terminals and the capacitor element connected to this pair of lead terminals, and a cutting process that cuts the side piece formation parts at the center position of the convex curved parts, and characterized in having a convex part and a concave part for forming the convex curved parts in the second press process.
Thereby, because the formation of the convex curved parts in the second press process can be carried out using the convex part and the concave part of the metal transfer mold used in the external resin packaging process, the metal transfer mold can also be used as a metal press mold for the formation of the convex curved parts. Thus, the number of metal molds can be reduced, the cost reduced, and in addition, the positional relation between the external resin packaging end part and the convex curved parts can be made to coincide easily.